Good safety practice has always dictated the use of a guard or protective device for personal safety on certain classes of tools having work engaging members which, because of their high speed of operation or exposed cutting edges, would allow serious injury to the operator should be accidentally contact the working engaging member. In particular, hand-held saws and grinders have long been known to constitute such a hazard, and for this reason saw and grinder manufacturers have provided numerous designs of guards for personal protection. However, a guard is effective only so long as it is used by the operator. In many instances, the inconvenience of the guard no matter how slight has prompted the operator to remove the guard while the tool is in service.
It is the purpose of this invention to minimize or eliminate the possibility of operating pressure fluid-driven tools such as a grinder without having the appropriate guard in place. The purpose of this invention is to provide an inexpensive and reliable interlock between the guard device and the tool. It is a further purpose of this invention to render the tool inoperable when the guard is not securely in place. It is a further purpose of this invention to interrupt the supply of pressure fluid whenever the guard is not secured to the tool. It is still a further purpose of this invention to render the tool incapable of being pressurized so long as the guard is not in place. These and other objects are accomplished by a pressure fluid-driven tool comprising: A tool housing; a pressure fluid supply connected to the housing; a pressure-fluid driven motor means in the housing communicating with the pressure fluid supply and having its work output on a spindle; a work engaging means mounted on the spindle; a guard means attached to the housing for at least partially surrounding the work means; and the attachment of the guard means being essential to the maintenance of the pressure fluid supply.